专题06 机械能守恒定律 能量守恒定律
目 录
01机械能转化及守恒的判断 2
考向一：机械能转化及守恒的判断 2
02 机械能守恒定律的应用 7
考向一：机械能的图像类问题 7
考向二：单个物体的机械能守恒 15
考向三：多个物体(系统)的机械能守恒 18
03能量转化及守恒定律的综合应用 20
考向一：能量转化及守恒定律的综合应用 20
考向四：涉及弹簧的能量问题 22
考向二：涉及板块、传送带的能量问题 33
01机械能转化及守恒的判断
考向一：机械能转化及守恒的判断
1．（2023·浙江·高考真题）一位游客正在体验蹦极，绑上蹦极专用的橡皮绳后从跳台纵身而下。游客从跳台下落直到最低点过程中（ ）
A．弹性势能减小 B．重力势能减小
C．机械能保持不变 D．绳一绷紧动能就开始减小
3．（2022·浙江·高考真题）神舟十三号飞船采用“快速返回技术”，在近地轨道上，返回舱脱离天和核心舱，在圆轨道环绕并择机返回地面。则（ ）
A．天和核心舱所处的圆轨道距地面高度越高，环绕速度越大
B．返回舱中的宇航员处于失重状态，不受地球的引力
C．质量不同的返回舱与天和核心舱可以在同一轨道运行
D．返回舱穿越大气层返回地面过程中，机械能守恒
5．（2021·浙江·高考真题）如图所示，同学们坐在相同的轮胎上，从倾角相同的平直雪道先后由同高度静止滑下，各轮胎与雪道间的动摩擦因数均相同，不计空气阻力。雪道上的同学们（ ）
A．沿雪道做匀速直线运动 B．下滑过程中机械能均守恒
C．前后间的距离随时间不断增大 D．所受重力沿雪道向下的分力相同
7．（2024·广东江门·统考模拟预测）蹦极是一项非常刺激的体育项目，而“反向蹦极”是一项比蹦极更加刺激的运动。如图所示，弹性轻绳上端固定在P点，下端固定在玩家的身上并向下拉长与固定在地面上的安全扣环相连。打开安全扣环后，玩家从c点开始由静止释放，像“火箭发射一般竖直向上运动”，上升到b点时速度最大，轻绳在a点为原长位置，玩家到达的最高点在P与a之间，不计空气阻力，下列说法正确的是（ ）
A．人在c到a运动过程中都做加速运动
B．人在c到b运动过程中做加速度减小的加速运动
C．在整个运动过程中，玩家的机械能守恒
D．人在b到最高点的运动过程中，玩家处于超重状态
8．（2024·广东惠州·统考二模）2023年10月3日，在杭州亚运会蹦床项目女子决赛中，中国选手朱雪莹夺冠，图为朱雪莹在东京奥运会上决赛时腾空后下落的照片，朱雪莹从刚接触床面到运动至最低点的过程中，下列说法正确的是（ ）
A．朱雪莹刚接触床面时速度最大
B．朱雪莹在该过程中始终处于失重状态
C．在该过程中朱雪莹的动能减少量等于弹性势能的增加量
D．在该过程中蹦床对朱雪莹一直做负功
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辕轰保2769怎样判断一个系统内机械能是否守恒 -
容熊雨13715094179 ______ 一个系统只有重力,或系统内的弹力做功时系统的机械能守恒.判断物体的机械能守恒是看是否有除重力和系统内的弹力以外的力做功,若外力使物体沿力的方向发生位移,则外力对物体做正功,则机械能增加,否则反之.
辕轰保2769如何判断机械能是否守衡 -
容熊雨13715094179 ______ 只有动能与势能之间的转化,没有摩擦之类就是机械能守恒
辕轰保2769物理必修2如何判断是否机械守恒 -
容熊雨13715094179 ______ 机械能守恒的定义:初状态的机械能(动能+势能)=末状态的机械能(动能+势能) 判断机械能守恒:从初状态到末状态的过程中,除开重力和弹簧的弹力,其他力做的总功为零,机械能守恒 几种机械能守恒的实例:不计空气阻力的情况下,任何的抛体运动(自由落体、平抛、竖直上抛、下抛、斜抛) 不计摩擦力和空气阻力的情况下,物体沿光滑斜面滑动(比如俯冲时的过山车) 不计空气阻力的情况下,用细线吊着的小球的自由摆动(单摆模型) 不计空气阻力的情况下,小球挂在弹簧上振动(弹簧模型) 不计摩擦力和空气阻力的情况下,小球在圆形管道内做圆周运动 天体(行星、卫星)的公转
辕轰保2769机械能守恒的判断 -
容熊雨13715094179 ______ 功能定理: 任何物体系统, 外力对其作的总功+系统内非保守力做的总功 = 系统的机械能(动能与势能之和)的增量. 所以, 情况一、机械能守恒. 情况二、机械能也守恒.
辕轰保2769如何判断系统机械能守恒?我知道怎么判断一件物体的机械能是否守恒,但我不知道怎么判断系统机械能是否守恒?是能量互相转化时就守恒吗? -
容熊雨13715094179 ______[答案] (1)做功条件分析法:机械能守恒 当发生动能与重力势能的转化时,只有重力做功,当发生动能与弹性势能的转化时,只有弹力做功,其他力均不做功,则系统的机械能守恒. (2)能量转换分析法: 若只有系统内物体间动能和重力势能及弹性势能的...
辕轰保2769怎么判断机械能是否守恒
容熊雨13715094179 ______ 第一看是否只有重力做功,如果是则守恒.第二其它力也做功不过它们只和为零,也就是有一个正功或者多个正功,有一负功或多个负功,不管多少其它力(不包括重力)做功为零的,机械能守恒.
辕轰保2769如何判断机械能守恒? -
容熊雨13715094179 ______ 一个系统里,如果只有保守力做功,则这个系统的机械能守恒.通常是重力,可恢复的弹力等.
辕轰保2769如何判断物体是否机械能,动能等守恒 -
容熊雨13715094179 ______[答案] 系统内只有弹力或重力做功或只有二者同时做功时机械能守恒. 根据Ek=mv²/2可得,对于同一物体,在保证机械能守恒的条件下,v不变即做匀速直线运动时动能守恒 希望对你有所帮助~有不懂的可以百度hi'我~
辕轰保2769如何判别机械能是否守恒
容熊雨13715094179 ______ 很简单,看机械能有没有转化为其他形式的能量 如有没有发热转化为内能,有没有发光转化为光能,有没有产生电流,转化为电能等 …… 有阻力,机械能就不守恒,会转化为内能(摩擦生热) 当然是电梯做的总功增加机械能,因为受外力作用电梯要经过一定位移,做功增加了机械能,同时重力做功增加了势能
辕轰保2769如何判断机械能守恒
容熊雨13715094179 ______ 物体机械能守恒条件是只有重力做功,系统是系统内只有重力和弹力做功,不能出现其他力做功,则机械能守恒
